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Topic Review (Newest First)

08-13-2004 05:09 PM

trees

If you are cruising at high RPM, you don't have a 3.08 rear. You should not be turning more than 2300 RPM at 70 MPH with a 3.08 gear If you have a Tach, then set 60 mph, and record your RPM and then go into the calculator Willys steered you to and compute your rear end ratio (RER). No tach? Then remove your cover or slide out your 3rd member and count the teeth on the ring gear (big gear) and Pinion (small gear) and divide the little number into the big number and the result is your gear ratio. I have never had good luck turning the rear wheels and counting drive shaft turns. Come up with a different answer each time I try it!!!

Trees

08-12-2004 06:47 PM

kd5boc

OK..."for dummies" so to speak...

1.) You have to rotate both tires at the same time (for 1 revolution) while you count the driveshaft.
2.) If you hold 1 tire and turn the other one, you must turn it twice to get the ratio...I seriously HOPE you don't have 6's...

willys36, thanks again I marked one tire and driveshaft and rotated the tire one complete full turn while watching the drive shaft turn a little over three times is how i can up with 3.08 ratio, i read someone else suggested two complete turns on wheel which would have given me 6.16, which is right? also i turn about 3500 rpm's @55mph is this because the 350 transmission instead of the rearend? thanks for your Patience.

08-12-2004 12:41 PM

willys36@aol.com

No, you are backward. For highway cruising you want a numerically lower gear ratio like 2.73 (They call that a 'high' gear - really confusing!). For quick acceleration you start going to numerically higher ratios like 3.54, 4.10 etc. Your 3.08 is actually a pretty good all-round compromise, with a bias to the highway cruiser side. Conversely, you would lean to the 3.54 - 3.75 region for a redlight bandit that could still be highway driven w/o screaming the driver out of his mind. 4.10 and on up is for 1/4 mile bursts only! Best of all worlds is to do what I am doing in my '53 Chevy pickup - 3.54 rear gears w/ 200R4 OD tranny w/ 0.71OD final ratio which gives an equivalent 2.51 rear ratio when in OD.

08-12-2004 11:31 AM

ricks032003

Thanks; sounds like i for sure have street gears maybe for street racing quick takeoffs from one red light to another? do you know what would be a good highway gear maybe like an 3.73? what do you suggest?

08-12-2004 11:23 AM

johnsongrass1

Higher numbers mean more acceleration and higher RPM.

Lower numbers mean less acceleration and lower RPM.

Finding a happy middle ground is the trick.

Street gears are typical 2:73 to 3:73

Track gears are typical 4:10 to 7:50

08-12-2004 11:11 AM

ricks032003

Thanks Willis but i still don't understand! is there anything a little easier for dummies?

Can anyone tell me if lower the ratio more RPM'S or higher? I have an streetrod with a 82 mustang rearend 7.5 3.08 limited slip which runs very high rpm's on the highway speeds, 350/350 drive train so what gears is recommed to lower rpm's 2000/2500 rpm's @70mph for highway use? thanks for everyone's help.